Tens of thousands of overweight children – some as young as four – will be
shipped off to fat camp, under a Government scheme to tackle obesity.

Primary school pupils identified as being overweight will automatically be offered a place on a state-funded diet and exercise scheme.

Although parents will have the right to refuse to send their children to the classes, ministers hope the majority will attend.

Parents groups said the new NHS rules meant Labour had moved "beyond a nanny state, to a dictatorship."

Health experts warned that the public branding of young children as fat could damage their confidence, expose them to bullying and trigger eating disorders. However, paediatricians welcomed the move.

Under existing regulations, children are weighed when they start primary school – aged four or five – and again as they leave, at 10 or 11. Parents of all children receive a letter saying whether their children are healthy, overweight, underweight or very overweight. Latest figures show that by the time they leave school, one in three children is overweight.

When it was introduced three years ago, the weighing programme was met with a backlash from parents. In its first year, more than half withdrew their children from the scheme, for fear they would be bullied after the class weigh-in.

When families were advised that pupils would not be told their weights, nor singled out and told to diet, but that data would simply be used by local health planners to monitor the spread of obesity and to help them set up the right services, participation rates increased. Last year, nine out of ten children were measured.

The new guidance, slipped out to NHS Primary Care Trusts in England during the school holidays, orders an immediate change of approach.

From this month, pupils whose weight is too high – or too low – will automatically be offered a referral to "weight management services" in areas which already run such programmes or can set them up quickly.

Existing NHS schemes range from 12-week weight loss courses taking place at weekends and on school nights, to six-week residential courses costing £3,000 a patient for the most obese.

All PCTs have been "strongly encouraged" to have children's weight management services in place by next September, so that every overweight child in England can be referred for diet and exercise sessions.

Those identified as obese may be sent to paediatricians for specialist treatment, drugs or even surgery.

Margaret Morrissey, founder of family lobby group Parents Outloud, said it was "unforgivable" to promote schemes which would inevitably encourage humiliation to be heaped on those children bused off to fat camps.

She said: "This has gone beyond a nanny state, beyond Big Brother."

"To label young children as overweight because they are carrying a few extra pounds makes them so vulnerable to bullying, and increases the risk of developing eating disorders, especially among the girls.

"Obviously it is unfortunate if parents feed their children badly but this Government appears to have forgotten that we do not live in a dictatorship."

Susan Ringwood, chief executive of eating disorder charity Beat, said she was "deeply concerned" that sending children to weight loss classes would increase the risk of bullying, which could trigger conditions like anorexia in the most vulnerable.

She said: "Children can be cruel, they exploit the weaknesses they find and we know that those who are bullied about their weight are more likely to develop disorders".

But paediatricians said the scale of the obesity crisis facing Britain meant that the drastic action being introduced by the Government was necessary.

Dr David Vickers, from the Royal College of Paediatrics and Child Health, said: "It seems to me that it is more outrageous to tell parents that their child is overweight then do nothing about it, than to send them a letter and then offer some support.

"Children who are overweight are already far more likely to be being bullied, I don't think enrolling them on these schemes will make that any worse."

Tam Fry, from the National Obesity Forum, said pupils should be weighed every year, and parents given detailed information about their body mass index so they could monitor their child, not a "badly written letter" filled with alarming warnings.

Even if a child is just one pound overweight, parents receive a standard NHS letter alerting them of an increased risk of cancer, diabetes and heart disease.

Latest figures show that by the start of primary school, 23 per cent of children are overweight, rising to 33 per cent by the time they leave.

If current trends continue, more than half the adult population will be obese by 2050, while spending on obesity will rise sevenfold, according to Government forecasts.

Currently, just a handful of PCTs automatically offer pupils a place on slimming programme if the school weigh-in finds they are overweight.

They include Nottingham City PCT, which runs a scheme which offers overweight pupils a place on a 12-week "Go 4 It" course which children and parents attend twice weekly, to take part in fitness sessions, and quizzes and games about nutrition, cooking and exercise.

Richard Warsop, from Nottingham, is one of the children who has benefited from the scheme. By the age of 12, Richard weighed 10 and a half stone.

With a height of 5 foot 2, that made him obese, according to charts of Body Mass Index – a recognised way of measuring how healthy someone's weight is compared to their size.

For years he had been bullied about his weight, culminating in an incident in which his nose was broken.

In the year since being referred to the Nottingham scheme, he has lost two stone, while he has grown to 5 foot 9.

His mother Alison says the boost to his self esteem from meeting other children in the same situation made the biggest difference to her son, who is now far more active, while the lessons for parents about health and nutrition opened her eyes to the family's unhealthy lifestyle.